In a conventional reciprocating internal combustion (RIC) engine, atomized liquid fuel and air are introduced into a cylinder through a port or valve, where the fuel/air mixture is ignited and burns rapidly during a single sweep of the piston in the cylinder. This occurs through a half-turn of the engine crankshaft and is conventionally referred to as a “power stroke.” FIG. 1A is schematic representation of such an engine stroke. In a conventional gasoline RIC engine, the fuel/air mixture is ignited with a spark, and in a Diesel engine, the compression of the mixture is high enough that ignition occurs without the aid of a spark.
The sweep or “stroke” of the piston down the cylinder, driven by the pressure of the burning gas, ends at the limit of the rotation of the crankshaft. When the piston has reached the low extreme of its movement in the cylinder, referred to as the “bottom dead center” (BDC) of the stroke, the highly-pressurized gas is released, bursting out into the atmosphere through a valve or port which opens in synchrony with the rotation of the crankshaft. This half-turn of the crankshaft is conventionally referred to as an “exhaust stroke.” FIG. 1B is schematic representation of such an engine stroke.
A conventional RIC engine converts the chemical potential energy of the fuel into mechanical energy and heat. Most of the heat energy produced is lost to the atmosphere in the exhaust gases which exit the combustion chamber directly to the atmosphere. At the point of exit, the combustion (exhaust) gases are very hot and at high pressure, thus containing a lot of energy.
As described above, the operation of a conventional RIC engine includes the unimpeded passage of exhaust gases from the combustion chamber to the atmosphere. Any restriction placed on the free exit of the exhaust gases reduces the efficient functioning of the engine which results from the rapid expansion of the gases at the point of exit, losing both pressure and heat, largely wasting the heat/pressure energy of the exhaust gases.
At the end of the exhaust stroke, when the piston has been carried to the top of the cylinder, all the energy contained in the exhaust gas has been dumped into the atmosphere and therefore lost. The inventive two-stage exhaust system disclosed herein avoids this wasteful loss of energy by introducing a means by which exhaust gases can exit the cylinder in two stages. The first stage diverts the high-pressure gases into a mechanical motor which can utilize such high-pressure gas as its driving force (source of energy). The second stage of the inventive exhaust system allows the free flow of residual exhaust gases to exit the engine in the normal manner.
A commonly-used turbine/compressor (turbocharger) connected to the exhaust manifold of a conventional RIC engine is designed to capture residual exhaust energy without restricting the flow of gases. These turbines change the flow direction of the high-velocity gases, and the resulting reaction is the spinning-up of the turbine, leaving the gas flow with diminished kinetic energy. In such a system, there is little pressure change in the turbine rotor blades, meaning that typically less than 5% of the energy in the exhaust is recovered. The present invention overcomes this limitation.
The inventive two-stage exhaust system produces two sources of power output from one source of fuel input. A conventional RIC engine produces only one source of power output from the fuel input, i.e., the rotational force produced at the engine crank. This is true even of the so-called hybrid RIC engines because the power output from these engines is still only produced at the flywheel. In this sense, these engines are not hybrid engines but only engines driving hybrid power-trains.
An engine with the inventive two-stage exhaust engine is a true hybrid engine. It produces two independent power outputs, the conventional mechanical power derived at the crankshaft plus the electrical power generated from first-stage exhaust gases, using no extra fuel. These two power outputs are not parasitic upon each other. The mechanical power produced at the crankshaft is not diminished by the electrical power drawn from the first-stage exhaust. This means there is a clear net addition to the power output of the two-stage exhaust engine.
The total energy output of a RIC engine, including all forms of energy produced, is 100% of the heat energy contained in the liquid fuel consumed by it, assuming complete combustion of the fuel in the cylinder. However, the best examples of RIC efficiency today can convert no more than 50% of this heat energy into mechanical energy; the remainder is lost. The use of the inventive two-stage exhaust system in a reciprocating internal combustion engine may increase the overall mechanical output of the RIC engine significantly, perhaps by as much as 40% or more, due to the ability of the inventive system to capture the immense gas pressure produced by the confined fuel/air combustion which is normally lost into the atmosphere in a conventional engine with a conventional exhaust valving system.
The inventive two-stage exhaust system greatly reduces the loss of the energy in the exhaust gas by allowing the high pressure energy contained in the “spent” combustion gases to be further converted into mechanical energy via a unique “jet port” or “jet valve” which directs a proportion of the high-energy combustion gases into a motor which can covert the high-pressure gas into electrical energy. The inventive two-stage exhaust system enables a RIC engine to function normally and efficiently without producing exhaust “back-pressures” which interfere with the proper, clean running of the RIC engine. Further, the two-stage exhaust system enables the design of the RIC engine to evolve into a new, more efficient class of prime mover.